1. Field of the Invention
This invention relates to an internal jet impingement type shell and tube heat exchanger, especially to an internal jet impingement type shell and tube heat exchanger in which the cooling jet tubes and the heating tubes are arranged together internally in the heat exchanger to conduct cooling by jet impingement in proximity area so as to increase heat transfer performance.
2. Brief Description of the Prior Art
So far, jet impingement cooling has been proved to be very efficient in cooling. However, it has been hardly seen in shell and tube heat exchanger due to the fact that liquid cooling medium is failed to impinge on the entire heat transfer surface, when the orifices are arranged on upper side of tube bundle. This will cause local dry-up effect on part of the heat transfer surface so that heat transfer efficiency becomes deteriorated. Generally, in a conventional prior art jet impingement cooling as shown in FIG. 6, four orifices are used to impinging cooling medium jet to the upper side of a staggered tube bundle having four rows. The heat transfer performance of the tubes of 2nd and 4th rows (from the upmost) is far worse than that of 1st (the upmost row) and 3rd rows, as the 1st row is directly impinged by cooling medium jet and the 3rd row, located right below the 1st row, is cooled by the cooling medium dropped from the 1st row. As few cooling medium is used to cool the 2nd and the 4th rows, heat transfer performance is quite low on those rows. Thus, if a denser arrangement of tube bundle is present in evaporator, the liquid drops jetted downward from orifices are not easy to impinge directly onto the lower tubes of the tube bundle.
In view of the above defect, inventor of the present invention has proposed a cooling medium collector, disclosed in Taiwanese Patent No. 344790, for the prevention of tube's dry-up as shown in FIG. 7 in which the cooling medium collector is fixed underside of each tube body. The cooling medium collector is an arc shape member on which clips are provided at both ends. The clips are spring clips of C shape which can clip on the tube body so that the associated arc shape member is able to be retained appropriately on each tube body. The cooling medium liquid coming down from both sides of the tube body enters into the gap between the tube body and the cooling medium collector. Therefore, the cooling medium liquid impinged on the upper part of each tube body and the cooling medium liquid accumulated on the collector forms an envelope on the tube body so as to avoid liquid dry-up on the tube body, in turn to achieve high heat transfer rate and to raise heat transfer efficiency. Thus, the liquid collector collects the liquid coming down along the periphery of each tube body and the liquid drops bouncing back so that the lower surface of each tube body can obtain sufficient cooling medium for cooling. In this manner, the occurrence of dry-up phenomenon is delayed or even eliminated. When the cooling medium collected by the collector is full, the overflow of cooling medium is designed to flow along an overflow guide and to fall onto the right upper side of the next row of tubes. Therefore, the incorporation of the liquid collector can raise heat transfer performance and attain high heat flux.
Encouraged by the success of the above liquid collector, inventor further proposes an internal jet impingement type shell and tube heat exchanger having its heat transfer performance superior than that of the above liquid collector, with a purpose to raise better heat transfer performance and attain higher heat flux.